(a) Field of the Invention
The invention relates to a character-carrying disc for a printing machine.
(b) Description of the Prior Art
It is known for such a character-carrying disc to comprise a movable member mounted on the body of the disc so as to be able to occupy on the one hand a working position in which it is engaged with a driving member of the machine intended to drive this disc in rotation, and on the other hand a retracted position in which it is clear from this driving member of the machine. The disc further comprises an elastic return device acting on said movable member and urging the latter into its working position, and a spring which co-operates with the element of the machine which mounts the disc so as to maintain the disc in place in the machine.
In known discs of this general character, the movable member by which the disc is rotatably driven by the machine is generally constituted by a pin. This pin is slidably mounted in a bore in a hub of the disc and is returned to its working position by a coil spring engaged thereon.
The manufacture of such discs is relatively expensive, especially by reason of the operations associated with the mounting of the retractable pin and of its return spring, as well as the mounting of the separate spring, generally a wire spring, which in use secures the disc on a shaft providing the mounting element of the printing machine.